At a semiconductor manufacturing factory, a variety of metal hydride gases and halide gases, such as silane, phosphine and arsine, are used during the semiconductor production. Since these gases are flammable and/or hazardous, from the standpoint of environmental protection, it is not allowed to discharge a waste gas containing such gases into the atmosphere without any treatment; therefore, it is required to perform a treatment in order to eliminate the danger and toxicity of such gases.
For treating such a discharge gas, there are a wet-type processing method and dry-type processing method. The former is a method in which a discharge gas is washed with a chemical solution, and such a wet-type processing method has drawbacks in that, since it uses water and drugs in large amounts, a large amount of wastewater must be treated after the processing, and that the equipments therefor are large and space-occupying. Meanwhile, the latter is a method in which a discharge gas is allowed to flow in a column loaded with a granular solid treatment agent and dangerous and hazardous gases are separated and detoxified by chemical actions between the gases to be detoxified and the treatment agent, that is, by absorption and/or chemical reactions. Such dry-type processing method is widely used in the treatment of a metal hydride-containing discharge gas or halide gas-containing discharge gas.
A number of patents are directed to a treatment agent of a metal hydride-containing discharge gas, and there are disclosed a detoxifying agent composed of a metal oxide (Patent Document 1), detoxifying agents composed of a metal hydroxide, metal carbonate or basic metal carbonate (Patent Documents 2, 3 and 4), detoxifying agents which comprise a metal hydroxide, metal carbonate or basic metal carbonate modified by a basic compound such as an alkaline metal (Patent Documents 5 and 6) and a detoxifying agent which utilizes a zeolite to eliminate phosphine (PH3) present in monosilane (SiH4) in a trace amount (Patent Document 7).
However, although such detoxifying agents composed of a metal hydroxide, metal carbonate or basic metal carbonate have excellent detoxifying capacities, an agent having a higher detoxifying capacity has been demanded due to the increasing usage of special gases in association with recent technological advance. Accordingly, the above-described detoxifying agents no longer have sufficient per-volume discharge gas-treating amount.
In the same manner, the per-volume discharge gas-treating amounts of those detoxifying agents which comprise a metal hydroxide, metal carbonate or basic metal carbonate modified by a basic compound such as an alkaline metal are also not sufficient. In addition, in cases where a detoxifying agent is produced in a large amount at an industrial scale by a method comprising the steps of mixing a powder detoxifying component and an alkaline component and molding the resulting mixture, since a strong alkali is used, there is a safety issue. Furthermore, in order to implement safety measures, there are various problems, for example, in that investments have to be made in a variety of equipments to have a closed system and such, so that the production cost is increased.    Patent Document 1: JP H05-269339A    Patent Document 2: JP H06-319945A    Patent Document 3: JP H08-192024A    Patent Document 4: Japanese Patent No. 2604991    Patent Document 5: JP H08-155259A    Patent Document 6: JP 2002-136834A    Patent Document 7: JP S62-212217A